Outburst Danger Research Articles

Investigating Food Safety Practices And Challenges In The Street Food Industry: A Comprehensive Study

Street food is a convenient and delicious option for those on the go. These delectable meals and refreshing drinks are willingly available from street vendors and hawkers, making them easily accessible to millions of urban customers. Particularly catering to individuals with limited incomes, street meals serve as a vital source of sustenance for their daily nutritional requirements. In many places of the world, there is still a danger of major food intoxication outbursts linked with street meals.

Division and Effect Evaluation of Fracking Outburst Elimination Zones in Surface Extraction Wells of Coalbed Methane

Surface hydraulic fracturing is an important measure for increasing reservoir permeability, which has advantages such as engineering safety and a large impact range and can be implemented ahead of the mine’s underground engineering. However, its underground outburst reduction range and effect are rarely reported, and there is a lack of connection with underground fracturing wells. Taking coalbed methane wells in the Lu’an Mining Area as an example, underground observation, microseismic monitoring, and numerical simulation methods were used to study the fracturing range and outburst control effect of surface wells. The fracturing zone of coalbed methane wells is approximately elliptical in shape, with the main fractures extending along the direction of the maximum horizontal principal stress. It can be divided into five zones: sand laying zone (radius of 140~150 m), fracture propagation zone (radius of about 180 m), fracturing fluid permeability zone (width of about 1 m), gas surge zone (width of 2~3 m), and final desorption zone (width of about 2 m). The stress around the fracturing zone increases along the direction of maximum and minimum principal stresses, while the stress value within the zone decreases, with a range of approximately 5~20% of the original geostress. The outburst reduction index Δh2 in the fracturing zone significantly decreased after fracturing. The percent of Δh2 (< 150 Pa) increased from 38.3% to 100% after fracturing. A model for evaluating the effectiveness of surface fracturing and outburst prevention was proposed, and the model was used in Tunliu Mine. The results showed that the standard‐reaching rate of extraction was high, and the danger of outburst could be completely eliminated. The research results can provide a reference for the arrangement of the coalbed methane wells and can also provide effective guidance for outburst prevention and control work during mining and excavation on a more macro scale. It provides a new idea and method for making up for the shortcomings such as the small impact range and safety hazards of underground fracturing.

Elimination mechanism of coal and gas outburst based on geo-dynamic system with stress–damage–seepage interactions

Coal and gas outburst is a complex dynamic disaster during coal underground mining. Revealing the disaster mechanism is of great significance for accurate prediction and prevention of coal and gas outburst. The geo-dynamic system of coal and gas outburst is proposed. The framework of geo-dynamic system is composed of gassy coal mass, geological dynamic environment and mining disturbance. Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in floor roadway. The results show the occurrence of outburst is divided into the evolution process of gestation, formation, development and termination of geo-dynamic system. The scale range of outburst occurrence is determined, which provides a spatial basis for the prevention and control of outburst. The formation criterion and instability criterion of coal and gas outburst are established. The formation criterion F1 is defined as the scale of the geo-dynamic system, and the instability criterion F2 is defined as the scale of the outburst geo-body. According to the geo-dynamic system, the elimination mechanism of coal and gas outburst—‘unloading + depressurization’ is established, and the gas extraction by boreholes through layer in floor roadway for outburst elimination is given. For the research case, when the gas extraction is 120 days, the gas pressure of the coal seam is reduced to below 0.4 MPa, and the outburst danger is eliminated effectively.

Research and Application of Comprehensive Early Warning System for Coal and Gas Outburst

Coal and gas outburst is an extremely complex dynamic phenomenon in the production process of coal mines. In order to further accelerate the intelligent construction of coal mines, taking Xinjing Coal Mine as an example, the online comprehensive analysis and warning indicator system and rules for coal and gas outburst applicable to Xinjing Coal Mine were studied, and a comprehensive warning system for coal and gas outburst in Xinjing Coal Mine was established. Through on-site application, it has been shown that the system has achieved real-time intelligent warning of the danger of outburst in the working face, standardized and dynamic management of outburst prevention information in the working face, as well as real-time dynamic update and sharing of outburst prevention information, improving the efficiency of mine outburst prevention management and the level of mine safety.

Coal and Gas Outburst Risk Assessment Using Cluster Analysis Method

Mining has historically been known as a high-risk industry. Coal and gas outbursts are one of the most significant accidents that occur in underground coal mines. Despite many years of research, the resources and mechanisms of this phenomenon are not well understood. Thus, it is difficult to forecast and control these events. As the mining depth and density increase, initial gas pressure and gas content of coal seams continue to increase, and the risk of explosion increases. Hence, explosion-prone areas expand gradually. As a result, a dynamic phenomenon has emerged in areas where there is no danger of outbursts. The risk of outbursts becomes more and more serious in coal mines. A coal outburst risk assessment includes evaluating the risk factors to what degree are present and then determining the risk areas of the mine. In this study, the Cluster Analysis method was implemented to identify the risk level of coal seams based on the evaluation of the outburst risk factors for an underground coal mine. Coal and gas outbursts occurring in Zonguldak hard coal basin were divided into two clusters, Cluster A and Cluster B. Coal seams in Cluster A were determined riskier than Cluster B coal seams.

A dynamic model of coalbed methane emission from boreholes in front of excavation working face: numerical model and its application.

China's current energy consumption is primarily fueled by coal, increasing coal mining with growing energy demand. Coal and gas outburst accidents are common problems in coal mining, and prediction methods are fundamental for preventing such accidents. The gas emission characteristics of boreholes are a combination of comprehensive coal properties and coal seam gas occurrence status; thus, the accurate prediction of gas emissions from boreholes is crucial for preventing such hazards. This paper presents a method for measuring the gas flow rate in continuous boreholes, which is used to predict outburst danger in front of the working face. The model was compared with field measurement data and found suitable for research. The effects of different initial gas pressures, different borehole radius, and different burial depths on gas emissions from boreholes were studied. The results showed that (1) initial gas pressure is the main influencing factor of gas gushing. The amount of gas emission during drilling and the attenuation of gas pressure are more sensitive to pressure. An increase in gas pressure considerably increases the amount of gas gushing out of drilling holes. (2) The increase in the drilling radius increases the generation of coal cuttings, the area of the drilling hole wall, and the degree of damage to the drilling hole wall. Consequently, the amount of gas gushing out of the drilling hole increases. (3) In situ stress occurs mainly because of the increase in gas pressure with an increase in burial depth and the increase in gas desorption caused by the increase in damage to the borehole wall. This study provides a new outburst prediction method, which involves identifying outburst hazards through the gas gushing out of the borehole. The results are expected to aid the control of underground coal and gas outbursts and ensure the safe production of coal mines.

Mental states dynamics in civilians during the war in Ukraine

The article presents the results of the mental states dynamics study in the Eastern region civilians of Ukraine during the Russian military aggression on the territory of Ukraine in the first year of the war. The paper substantiates the relevance of the study of the mental states of the civilian population in the context of maintaining mental health problem and preventing post-traumatic stress disorders. War is a prolonged traumatic situation during which episodes of a threat to life and health occur with a certain frequency, and this affects the dynamics of the mental states of the civilian population. An additional traumatic effect on the psyche is exerted by the information and psychological warfare that people are exposed to through Internet technologies. The study found that at the beginning of hostilities in Ukraine, the most typical mental states of civilians in the eastern regions of Ukraine were fear, confusion, helplessness, despondency, depression, panic, irritability and anger. These mental states are typical of the acute experience of a traumatic stressful situation. A year after the start of the war, respondents noted a significant decrease in the frequency of experiencing fear, confusion and panic. At the same time, sadness, depression, fatigue, exhaustion, anxiety, and irritability became common. These are mental states that testify to the reduced energy potential of the population, the danger of new fears and outbursts of irritation. The consequence of this may be a violation of interpersonal relationships, professional maladjustment, the development of psychosomatic and post-traumatic disorders. At the same time, a number of respondents showed an interest in life, "protective indifference", peace. The results of the study can be used in the development of psychotechnologies to minimize the consequences of war-related injuries, as well as to preserve and support the mental health of the population in war conditions and in the long term.

A New Method to Predict Shock-Type Coal-Gas Outburst Disaster and Its Application

Coal-gas outburst is the one of most serious coal mine dynamic disasters which affects safety mining, with 39 deaths reported during 2019 in China. The mechanism of coal-gas outbursts is complex, and the prediction methods are immature at present. This article was based on previous research results. Firstly, the occurrence mechanism of coal-gas outburst disasters was summarized. It is clear that the occurrence of coal-gas outburst disasters is jointly affected based on the stability of the static structure of coal-rock, the gas parameters, and the release intensity of shock stress. Secondly, the stability evaluation models of coal-rock static structure, gas parameters, and shock stress release intensity were built, respectively, based on the influence factors. Then they were coupled and supposed to form a new prediction model. Finally, the prediction method was applied to the Ji15-17200 working face of No.12 coal mine in Pingmei company. The working face was divided into three danger levels including weak outburst danger area, medium outburst danger area, and strong outburst danger area. The accuracy of the predicted results was analyzed based on the actual mining condition of the Ji15-17200 working face. The results show that prediction accuracy is high, and it can be used for actual applications. The research results are of guiding significance to better prevent and control coal-gas outburst accidents and ensure safe production in coal mines.

Gas pressure evolution characteristics of deep true triaxial coal and gas outburst based on acoustic emission monitoring

Coal and gas outburst is one of the geological disasters that seriously threaten the safety of coal mines production. In recent years, with the increase of mining depth, outbursts become frequent. To further explore the occurrence mechanism of deep coal and gas outburst, a self-developed true triaxial coal and gas outburst simulation device was used to simulate the coal and gas outburst at different depths. The results show that with the increase of simulation depth, the critical gas pressure of outburst gradually decreases, and the unit outburst intensity increases sharply. The gas threshold of deep coal and gas outburst is lower. During the incubation and excitation, gas pressure has three special variation rules, namely self-increasing characteristic, stage and instantaneous. In the early incubation, acoustic emission (AE) energy is at a low level, low energy frequency is dominant; in the later incubation, AE energy increases greatly, high energy frequency is dominant. From the perspective of AE energy, a quantitative index that reflects the danger of coal and gas outburst in the incubation is defined, which provides a scientific reference for the prediction and prevention of disasters of coal and gas outburst in deep mining.

Quantitative Evaluation of Complex Degree of Geological Structure in Yangquan Mining Area

The study and analysis of tectonic activities on regional structures is of great significance to mine prospecting and production safety in mine work. We take the No. 3 coal seam in the Yangquan mining area as the object of study. The methods of fractal dimension, structural curvature and trend surface analysis are applied to quantitatively evaluate and predict the mine structure. The folded meso-plane analysis is also carried out. The results show that the trend surface reflects that the monoclinic structure is high in the NE direction and low in the SW direction. The dip angle is small, and the overall structure is characterized by an NNE−NE trend. The curvature value of the coal seam in the mining area is generally small. The northwest structure is relatively simple. The eastern fracture is more developed. The southern structure is relatively simple. A large nearly EW direction Taohe syncline is developed in the middle and south. Several large fractures in the NE direction are developed in the southwest. The capacity dimension of fractures in the mine field is mostly between 0.6 and 1.6. It indicates that the complexity of the fracture structure in the mine field has obvious heterogeneity. The neutral surface of the mine is in the third section of Taiyuan formation, and the No. 3 coal seam is above it. The research results have reference significance for the evaluation and prediction of safe mining and gas outburst danger zones in mining areas.

Substantiation of informational system for coal seam outburst danger continuous prediction with high level of the result veracity

The application feld, the construction principle, the content of data system for coal seam outburst danger continuous prediction and its integration with the subsystems of a coal mine multifunctional safety system are substantiated. Widely known models for initiating gas-dynamic phenomena in underground mines are analyzed. It is shown that to describe the process of sudden coal and gas outburst preparation the most suitable model is the one that consists of two stages: the creation of a coal block structure by means of developing the crack system (the frst stage) and squeezing the blocks out of the mouth of the future outburst cavity (the second stage). Basic factors important for reliable prediction of outburst danger are substantiated on their basis. The infuence of failing to take into account the basic factors of the outburst danger for some instrumental and geophysical methods of prediction is analyzed. It is demonstrated that the most reliable geophysical method, at present, is the spectral-acoustic one. The description of the procedure for experimental determination of the outburst danger limit value indicator for this method and for certain coal workings is introduces.

Coal Seam Gas Extraction by Integrated Drillings and Punchings from the Floor Roadway considering Hydraulic-Mechanical Coupling Effect

Owing to the exhaustion of shallow coal resources, deep mining has been occupied in coal mines. Deep buried coal seams are featured by the great ground stress, high gas pressure, and low permeability, which boost the risk of gas disasters and thus dramatically threaten the security about coal mines. Coal seam gas pressure and gas content can be decreased by gas extraction, which is the primary measure to prevent and control mine gas disasters. The coal mass is simplified into a continuous medium with dual structure of pores and fractures and single permeability. In consideration of the combined effects of gas slippage and two-phase flow, a hydraulic-mechanical coupling model for gas migration in coals is proposed. This model involves the equations of gas sorption and diffusion, gas and water seepage, coal deformation, and evolution of porosity and permeability. Based on these, the procedure of gas extraction through the floor roadway combined with hydraulic punching and ordinary drainage holes was simulated, and the gas extraction results were used to evaluate the outburst danger of roadway excavation and to verify the engineering practice. Results show that gas extraction can reduce coal seam gas pressure and slow down the rate of gas release, and the established hydraulic-mechanical coupling model can accurately reveal the law of gas extraction by drilling and punching boreholes. After adopting the gas extraction technology of drilling and hydraulic punching from the floor roadway, the remaining gas pressure and gas content are reduced to lower than 0.5 MPa and 5.68 m3/t, respectively. The achievements set a theoretical foundation to the application of drilling and punching integrated technology to enhance gas extraction.

Study on the coal damage effects caused by the CO2-alkaline water two-phase displacing gas and wetting coal

The technique of CO2-alkaline water two-phase displacing gas and wetting coal can effectively prevent the risk of coal and gas outburst, while it will damage coal under the erosion of both acid and alkali. To explore the influence of this measure on the physical and chemical properties of coal, the variations of minerals and micro-structures in different coal samples were tested with several research methods including the XRD, XRF and FTIR. The results showed that, after adopting this method, the content of kaolinite and AI, Si and S decreased to different extent, and the content of carbonate, C and Na increased clearly. In the immersed water of DL, ZX and XT coal samples, the HCO3– disappeared completely, the Ca2+ and Mg2+ decreased markedly, while the content of CO32– increased observably, with the increment of 88.7%, 85.3%, 77.7%. The micro-structure in coal was more developed, there were more granular minerals distributed on the surface of coal, and the number and diameter of pore structure all rose. The total volume and the average diameter of pore structure in three coal samples increased distinctly, with the increment of 87.5%, 62.5%, 37.5% and 121.8%, 8.5%, 20.3%, respectively. In addition, the proportion of oxygen-containing functional groups in three coal samples increased significantly, with the increment of 11.4%, 41.4% and 4.5%. Therefore, this measure can obviously improve the effects of water injection, the hydrophily, and the water-holding capacity of coal, more effectively prevent the danger of coal and gas outburst.

Substantiation of outburst danger automated monitoring on amplitude frequency characteristic median of the operating equipment noise and methane concentration in the mine working medium

Basic requirements to the methods of current outburst danger prediction are formulated. The methods must be applied in the process of mining not interfering with the works and taking into account basic factors that cause the outbursts and they should have scientifically grounded methodology for fast definition of outburst danger criteria under certain mining, geological and engineering conditions. It is shown that geophysical prediction methods can meet the first requirement. Rock pressure, in-situ gas pressure and coal strength are taken as basic factors of outburst danger. Some well-known geophysical method such as a method of acoustic emission, a spectral-acoustic method, a gas analytical method and a temperature method taken separately do not satisfy the second and the third requirements. That is why it is suggested controlling rock pressure by spectral-acoustic method, gas pressure by means of gas analyser on methane concentration at the face of the working while mining coal and coal strength should be measured by a strength measuring device. To improve the accuracy of the prediction a version of spectral-acoustic method based on dependency of amplitude-frequency characteristic median of mining operating equipment noise on average stresses at the section between the source of the noise and geophone. The criterion of outburst danger is substantiated and the algorithm for arranging automated monitoring of coal seam outburst danger is offered.

Outburst danger criteria for acoustic prediction methods at the initial and final stages of preparing sudden coal and gas outburst

Two stages of preparing coal and gas outburst are studied in the article. At the first stage the cracks which create a coal block structure are being developed ahead of the moving workings in a zone of high rock pressure. At the second stage the crashing of a narrow coal layer in the mouth of starting outburst cavity and its outsqueezing into the workings takes place. The control of cracks development is fulfilled by acoustic emission method. For controlling the rock pressure spectral-acoustic method is applied. The outburst danger criterion of spectral-acoustic method is corrected depending on the coal strength and in-situ pressure and they are estimated according to the methane concentration in the workings atmosphere. The results of outburst danger criteria comparison for different variants of spectral-acoustic method in a form of relation between high frequency and low-frequency amplitudes of the operating equipment “noise” spectrum and in the form of current and critical values of amplitude-frequency characteristic medians of noise are introduced. It is demonstrated that a crack development criterion and the criterion of a coal layer outsqueezing coincide if there is no gas in a coal seam. With the increasing of methane concentration at the face the crack development criteria decrease much faster than outsqueezing criterion. It is concluded that the result of the outburst danger prediction made by acoustic emission method is a necessary but not sufficient condition for initiating the outburst. The prediction, made by acoustic emission method supplemented by controlling methane concentration and coal strength allows estimating outburst danger within the whole process of outburst preparation.

Application of multi-source information intelligent early warning system for coal and gas outburst

The construction and application of a multi-source information comprehensive early warning system for coal and gas outburst in Xinjing Mine is described. First of all, through a large number of statistical analysis work of mine gas dynamic phenomenon, master the internal laws and characteristics of coal and gas outburst events in Xinjing mine, and use scientific reasoning and analysis methods to establish a multi-source information alarm index system in line with the actual situation of the mine. Secondly, design a professional and efficient early warning data chain structure. Finally, from the information collection end, professional analysis subsystem, the intelligent early warning system is built in three aspects of database to realize the online monitoring, intelligent identification and real-time early warning of prominent hazards. The overall accuracy of the early warning system in Xinjing Mine test period is over 91%, the overall false alarm rate of no outburst danger is less than 9%, and there is no occurrence of the phenomenon of no outburst danger, so the system has a high accuracy of early warning.

A fully multifield coupling model of gas extraction and air leakage for in-seam borehole

Air leakage around the in-seam borehole leads to a poor quality of gas extracted, thus gas outburst danger is difficult to eliminate but also may cause other disasters, such as coal spontaneous combustion and gas explosion. Moreover, the low concentration gas discharged into the atmosphere always possesses an intense greenhouse effect. To investigate multiphase and multifield coupling problem of gas extraction, a dual medium coupling model was developed in this study to describe the gas–air mixture flow by considering the influences of matrix shrinkage and effective stress on coal permeability. And the coupling model was calculated by the 3D numerical simulation and presented an ideal matching result with the field data. Then, the key factors affecting the gas extraction quality were also investigated with the model. It was found that the gas concentration elevated with the increase in the sealing length and borehole diameter, and reduced with the augmentation of extraction negative pressure and coal permeability. Therefore, we developed an improved sealing technology, which can fully seal the various fractures around the borehole for improving gas extraction. The field test indicated that the gas concentration by this improved sealing technology was 1.91 times that of the traditional sealing method, and still maintained a relatively high extraction level in the subsequent extraction stage with a superior application effect. The results of this work can help in optimizing the borehole sealing technology for improving gas extraction quality, which is of great significance to CBM exploitation and utilization, reduce greenhouse gas emission and ensure safe mining.

Construction and application of gas emission feature outburst early warning system in working face

In order to realize the accurate early warning of coal and gas outburst in Xinyuan Coal Mine, the early warning system of coal and gas outburst based on the dynamic characteristics of gas emission is constructed by using the dynamic characteristics of gas emission. The results show that the outburst early warning system based on the characteristics of gas emission can realize the real-time and dynamic early warning of the outburst danger of the working face of Xinyuan Mine, and the early warning accuracy is up to 79%, which ensures the daily safety production of Xinyuan Mine.

Elimination of Coal and Gas Outburst Dynamic Disasters in Dengfeng Coalfield through Gas Extraction Based on Extremely Thin Protective Coal Seam Mining

No. 21 coal seam is a full‐thickness structured soft coal in Dengfeng coalfield. The coal seam gas‐bearing capacity is high, and the permeability is poor, thus resulting in serious coal and gas outburst dynamic disasters. According to the gas geological conditions of Baoyushan Mine, No. 17 coal seam without outburst danger, which is 0.5 m thick and 23.4 m under No. 21 coal seam, was mined in advance as the lower protective seam. At the same time, a gas extraction roadway was constructed in No. 21 coal seam floor. Cross‐layer boreholes were constructed to extract the pressure relief gas of No. 21 coal seam for comprehensive treatment of mine gas. The mobile deformation of the overburden coal and rock mass after mining No. 17 coal seam, the fracture development characteristics of No. 21 coal seam, the pressure relief gas migration of the coal seam, the gas extraction, and the outburst danger elimination were studied. The research findings showed the following: (1) after mining No. 17 coal seam, the overburden hard and extremely thick limestone roof sagged slowly, albeit leading to no craving zone. (2) The permeability of No. 21 coal seam was increased by about 394 times, from 0.0012 mD to 0.4732 mD. (3) After the extraction of pressure relief gas through the gas extraction roadway on the floor through the cross‐layer borehole, the gas pressure of No. 21 coal seam decreased from 1.17 MPa to 0.12 MPa, while the gas content decreased from 9.74 m3/t to 3.1 m3/t, which suggested that the coal and gas outburst dynamic danger of No. 21 coal seam was totally eliminated and the goal of safe and efficient mining in the mine was realized.

Investigation of Tectonically Disturbed Zones of Coal Seams of the Kuznetsk Coal Basin Using SANS

Small-angle neutron scattering (SANS), low-temperature nitrogen adsorption (Brunauer–Emmett–Teller method, or BET) and Raman spectroscopy are used for a comparative analysis of the structural characteristics of the coals of the two seams, Boldyrevsky and Polenovsky, of the Kuznetsk coal basin. SANS measurements show that the microstructure of coal is characterized by surface fractal dimension close to three. The calculated specific surface area of the pore space makes it possible to distinguish the zones of disturbances from the calm areas of the same coal seams. The most sensitive method for the analysis of tectonic disturbances is the Raman spectroscopy, which allows tracing the characteristics of the type of deformation (brittle or ductile) in the disturbed zones. The BET and SANS methods are necessary to understand the dependence of coal Raman spectra on disturbances. Thus, an increase in specific surface area and surface fractal dimensions indicates the potential danger of outbursts in the area of the tectonic disturbances.